Voltage Dips Influence Zone and Propagation
through the Industrial Facility
Abstract-- Voltage dips and short interruptions are mainly
caused by the short circuit in transmission and distribution
network. In this paper it is given the calculation of short circuits
influence zone in transmission network affecting the depth of
voltage dip in the examined node. There is also given the
calculation of voltage dip propagation inside the examined
industrial facility for the case of one-phase short circuit. The
check of the influence zone and voltage dip propagation is
experimental confirmed by measurements made in one-month
period.
Index Terms—Voltage Dip, Short Circuit, Transmission
Network, Induction Motor, Contactor, Industrial Facility,
Measurements
I. INTRODUCTION
Voltage dips and short interruptions are considered to be
the dominant power quality problem in the industrial facilities
[1], [2]. Different kinds of electrical equipments and
appliances have not the same sensitivity on voltage dips and
short interruptions. Typical examples of sensitive equipment
are DC and AC drives, electronic equipment, controllers, and
others.
Some of the most important electrical loads in industrial
facilities, often very sensitive to voltage dips and short
interruptions, are induction motors and motor contactors. The
case of a series of induction motors included into production
line is especially problematic and frequent. In that case the trip
of even only one - the most sensitive motor - technologically
conditions the disconnection of a series of other motors, i.e.
the trip of the complete production line [3], [4].
Voltage dips and short interruptions are mainly caused by
the short circuit in adjacent transmission and distribution
network. In some industrial facilities voltage dips are caused
by large induction motor starting or switching operations
(transformers, capacitors).
In this paper it is given the calculation of short circuits
influence zone in the transmission network affecting the depth
R. Goic is with the Department of Power System Engineering, Faculty of
Electrical Engineering, Mechanical Engineering and Naval Architecture,
University of Split, R. Boskovica b.b., 21000 Split, Croatia (e-mail:
rgoic@fesb.hr)
E. Mudnic is with the Department of Electronics, Faculty of Electrical
Engineering, Mechanical Engineering and Naval Architecture, University of
Split, R. Boskovica b.b., 21000 Split, Croatia (e-mail: emudnic@fesb.hr)
M. Lovric is with HEP Transmission System Operator, South Department,
Lj. Posavskog 5, 21000 Split, Croatia (e-mail: marko.lovric@hep.hr)
Eugen Mudnic,
Marko Lovric
of voltage dip in the examined node with the industrial facility
connected. Also, it is given the calculation of voltage dip
propagation inside the examined industrial facility for the case
of one-phase short circuit as the most frequent cause of
voltage dip. The experimental check of calculations is
confirmed by measurements taken with numerical relays,
which registered voltage dips on each voltage level in the
factory.
II. THE INFLUENCE ZONE
According to IEC definitions, the short interruption is a
sudden reduction of the voltage on all phases at a particular
point on an electricity supply system below an interruption
threshold (usually 10% of nominal voltage) followed by its
restoration after a brief interval. Accordingly, the voltage dip
is a sudden voltage reduction at a particular point on an
electricity supply system below a dip threshold (usually 90%
of nominal voltage) followed by its recovery after a brief
interval. The above definitions are shown in Figure 1.
V (p.u.)
1,01
Duration
0,8
0.8
Voltage in pu
Ranko Goic, Member, IEEE,
0.6
0,6
Treshold
Depth
0.4
0,4
0.2
0,2
0
Retained voltage
00
50
1
100
2
150
3
Time in tcycles
( ms)
200
4
250
5
300
6
Fig. 1. Definitions of voltage dip terms
The voltage dip duration or the interruption duration is
determined by the protection time response. It regularly
amounts up to a few hundreds of milliseconds for the fault in
transmission network, while in distribution network it can last
even up to a few seconds.
Faults in transmission networks are cleared by the faulted
network element protection. Meanwhile, in the large area of
surrounding transmission network the voltage in faulted phase
drops to value between 0 and 1 p.u., depending on “electrical
distance” from the fault location. The resulting voltage dip is
transferred to all connected distribution and industrial
networks. The similar situation happens with faults in
distribution and industrial (customers) networks, but resulting
voltage dip usually affects small adjacent network area.
The influence zone is considered the area of transmission
network and possibly distribution network where the short
circuit causes voltage dip or short interruption in the examined
node. The influence zone is defined according to the depth of
voltage dip. The short circuit in the immediate vicinity of the
examined node causes short interruption, while the depth of
voltage dip in the case of a distant short circuit depends on the
electrical distance of the fault point from the examined node.
The influence zone is set for the discrete range of the voltage
dip depth, thus defining the surrounding network area where
the fault will cause the voltage dip of the examined span [5].
Determining the influence zone is the basis for the stochastic
prediction of voltage dips caused by faults in transmission
network. Combined with statistical data about annual number
of faults per km of transmission line, the expected frequency
of voltage dips can be calculated with the given magnitude.
The example of calculation is given for 110 kV node of
transformer station Kastela 110/35/10 kV. The two cement
factories are connected to this node by 35 kV cables and two
110/35 kV transformers. The calculation is done by the
PowerCAD software [6], simulating short circuits on the
transmission network model, i.e. by the voltage response
during fault in the examined node.
MELINE
GRAČAC
The influence zone is calculated for the three-phase and onephase short circuit in two cases:
• maximal short circuit power when all the generators in
the adjacent hydro power plants are connected, working
with nominal power
• minimal short circuit power when the minimal number of
generators in the adjacent hydro power plants is
connected
Selection of these characteristics cases is motivated by
different short circuit power level depending on number of
hydro generators connected to transmission network. In winter
time daily all hydro generators are usually in operation (about
2000 MVA in radius of 200 km). On the other side, in summer
time nightly, only a few hydro generators are in operation
(100-300 MVA).
The calculated influence zone for the one-phase short
circuit during the maximal and minimal short circuit power is
shown in Figure 2 and Figure 3 respectively. The selected
zones are for the calculation 0-10% (short interruption), 1050%, and 50-80%.
BOS.GRAHOVO
HPP MILJACKA
BRINJE
EVP STRMICA
RAB
HPP GOLUBIĆ
L.OSIK
EVP KNIN
KS TORETA
KS VAŠIBAKA
KNIN
HPP VELEBIT
KS DEDA
HPP PERUČA
KS KOROMAČINA
NOVALJA
PAG
PPS BUŠKO BLATO
LIVNO
OBROVAC
KS SELINA
SINJ
KS KULINA
NIN
KS BILI BRIG
ZADAR CENTAR
BENKOVAC
ZADAR
RS LOZOVAC
HPP ORLOVAC
BIOGRAD
KONJSKO
MOSTAR 400
BILICE
MOSTAR 220
RAŽINE
KAŠTELA
LEGEND:
TROGIR
DUJMOVAČA
SUĆIDAR
GRUDE
IMOTSKI
METERIZE
TS 400/220/110kV
KRALJEVAC
HPP ZAKUČAC
TS 220/110kV
KS PUJANKE
TS 110/XkV
TS 35/10kV
VISOKA
HPP
CS 110kV
400kV
220kV
110kV
110kV (35kV)
30kV
HPP ĐALE
VRBORAN
DUGI RAT
HPP KRALJEVAC
KS DUGI RAT
KS POSTIRA
KS LOZNA MALA
MAKARSKA
NEREŽIŠČA
0-10 %
KS SLATINA
OPUZEN
ČAPLJINA
EVP OPUZEN
10-50 %
KS TRAVNA
NEUM
STARI GRAD
STON
KS MEDVEDBAD
50-80 %
KS PERNA
KS PAPRATNA
BLATO
KS STREČICA
KOMOLAC
TREBINJE
TREBINJE
TREBINJE
HPP DUBROVNIK
Fig. 2. Voltage dip influence zone in the node Kastela, caused by one-phase short circuit during maximum short circuit power
MELINE
GRAČAC
BOS.GRAHOVO
HPP MILJACKA
BRINJE
EVP STRMICA
RAB
HPP GOLUBIĆ
L.OSIK
EVP KNIN
KS TORETA
KS VAŠIBAKA
KNIN
HPP VELEBIT
KS DEDA
HPP PERUČA
KS KOROMAČINA
NOVALJA
PAG
PPS BUŠKO BLATO
LIVNO
OBROVAC
KS SELINA
SINJ
KS KULINA
NIN
KS BILI BRIG
ZADAR CENTAR
BENKOVAC
ZADAR
RS LOZOVAC
HPP ORLOVAC
BIOGRAD
KONJSKO
MOSTAR 400
BILICE
MOSTAR 220
RAŽINE
KAŠTELA
LEGEND:
TROGIR
IMOTSKI
METERIZE
TS 400/220/110kV
DUJMOVAČA
SUĆIDAR
GRUDE
KRALJEVAC
HPP ZAKUČAC
TS 220/110kV
KS PUJANKE
TS 110/XkV
TS 35/10kV
VISOKA
HPP
CS 110kV
HPP ĐALE
400kV
220kV
110kV
110kV (35kV)
30kV
DUGI RAT
VRBORAN
HPP KRALJEVAC
KS DUGI RAT
KS POSTIRA
KS LOZNA MALA
MAKARSKA
NEREŽIŠČA
0-10 %
KS SLATINA
OPUZEN
ČAPLJINA
EVP OPUZEN
10-50 %
KS TRAVNA
NEUM
STARI GRAD
STON
KS MEDVEDBAD
50-80 %
KS PERNA
KS PAPRATNA
BLATO
KS STREČICA
KOMOLAC
TREBINJE
TREBINJE
TREBINJE
HPP DUBROVNIK
Fig. 3. Voltage dip influence zone in the node Kastela, caused by one-phase short circuit during minimum short circuit power
III. VOLTAGE DIP PROPAGATION INSIDE THE INDUSTRIAL
FACILITY
The larger one of the two cement factories has the
approximate constant load 31 MW, with more than 70% taken
by large induction motors. The trips of large induction motors
are very frequent in the factory, primarily due to voltage dips.
In the year 2001 in total there were registered 175 trips.
Generally, every voltage dip with depth larger than 10%
causes interruption in hot production line. The new starting of
the production sometimes can last for a few hours. The
consequences of numerous trips are large production losses
due to the suspended operation.
Large induction motors are connected to 6 kV voltage by
two 35/6 kV transformers. The largest induction motor
(driving the ventilator) has a nominal power of 2000 kW. All
motor contactors are connected to control voltage circuit,
supplied by one-phase transformer 380/220 V. It is supplied
from the line voltage of a 6/0.4 kV transformer.
Figure 4 shows the calculation of voltage dip propagation
on voltage levels inside the factory. The voltage dip for the
case of one-phase short circuit in transmission network is
assumed to be resulting with retained voltage of 11% in the
faulted phase. Because of wye/delta winding connection of
35/6 kV transformer, one-phase dip on 35 kV voltage level is
transferred to 6 kV-side as two-phase dip. Delta/wye winding
connection of 6/0.4 kV transformer causes the transfer to 0.4
kV voltage level again as one-phase dip.
The voltage dip transfer to 220 V control voltage circuit
depends on the phase in which short circuit occurred in
transmission network:
• If it occurred in the R phase, the voltage dip is not
transferred to the control voltage circuit.
• If it occurred in the S or the T phase, the voltage dip is
transferred to the control voltage circuit with the retained
voltage of 68%.
Voltage dip sensitivity of most contactors causes the
disconnection of induction motors at every dip with retained
voltage under 85-90%. But during voltage dips caused by onephase short circuit in related influence zone, 2/3 of such faults
will be followed by disconnection of contactors, and 1/3 faults
will remain with contactors closed. There can appear two
main problems:
• Sometimes sensitivity of contactors causes disconnection
of induction motors although this disconnection is not
necessary for motor protection (voltage dips with smaller
depth and short duration are not dangerous for induction
motors).
• Disconnections are not selective: 1/3 of voltage dips
remain invisible to contactors regardless of depth, and, if
there is no other protection, there is possibility of motor
damage.
Transmission network
One-phase
short circuit,
TS Konjsko
IV. EXPERIMENTAL CHECK OF INFLUENCE ZONE AND VOLTAGE
Vt
Vr
Vr: 11%
Vs: 97%
Vt: 94%
Vr
Vr: 40%
Vs: 89%
Vt: 89%
Vr
Vr: 68%
Vs: 100%
Vt: 68%
Vr
Vr: 90%
Vs: 90%
Vt: 54%
110 kV
Vs
TS 110/35 kV
Kastela
35 kV
Vt
...
Cable 35 kV (2x)
Cement factory
Vs
35 kV
TS 35/6 kV (2x)
Vt
6 kV
...
Vs
Vt
TS 6/0.4 kV
R
S
T
0.4 kV
TS 380/220V
Vs
F
0
Control
voltage 220V~
Vf
Vf: 100%
For short circuit in phase r
Vf
Vf: 68%
For short circuit in phase s
Vf
Vf: 68%
For short circuit in phase t
DIP PROPAGATION
The check of the influence zone and voltage dip
propagation is experimental confirmed by measurements made
in one-month period according to the scheme shown in Figure
5. The measurements are taken by 6 numerical relays, which
registered voltage and current waveforms 100ms before and
3s after:
• voltage drops below 10% of nominal voltage
• every circuit breaker operation.
Measured waveforms were line-to-line and phase voltages
on each voltage level in the factory, control voltage, currents
of 35 kV supply cables, currents of 35/6 kV transformers, and
the most sensitive induction motors currents. They were
programmed to start the registration of voltages and currents
simultaneously: the activation of each relay generated the
signal for the activation of all other relays.
Contemporary, the data about faults in adjacent
transmission network, with exact location, type and duration,
are collected in local transmission network control centre.
Every voltage dip registered by relays was compared to the
calculated values of voltage dip propagation on network
model, assuming the exact location and type of fault in
transmission network. The difference between the model
results and the voltage dips measured values at all voltage
levels in the cement factory were in range of 4-9%.
Fig. 4. One-phase voltage dip propagation to all voltage levels inside the
cement factory
Cable 35 kV (to another factory)
Cables 35 kV
(supply)
Ir,Is,It
Measurement A
Ir,Is,It
Vr,Vs,Vt
Ir,Is,It
Measurement B
Ir,Is,It
Ir
Measurement D
Vr,Vs,Vt
Ir,Is,It
Ir,It
Measurement C
Control voltage
Measurement E
Vr,Vs,Vt
Ir,Is,It
Urs,Ust
Ir,Is,It
Control voltage
Fig. 5. Voltage and current measurement
Measurement F
A characteristic example of voltage dip recorded during the
measuring period is shown in Figure 6 and Figure 7. Figure 6
shows the RMS values of phase voltages 6 kV before, during
and after voltage dip, as well as the voltage phase diagram
before and during voltage dip. The RMS values of secondary
side phase currents of one transformer 35/6 kV are shown in
Figure 7. The current phase diagram is shown for both
transformers (induction motors supplied from the second
transformers were not in operation).
This was a typical case of voltage dip caused by one-phase
short circuit in transmission network, transferred on 6 kV
busbars in cement factory as a two-phase voltage dip with
98%, 60%, and 58% retained voltage. The voltage dip
duration was about 100ms, which is also a typical response
time for the distant protection of 110 kV line affected by fault.
Maximal RMS value of currents during voltage dip was
325%, 145%, and 205% in relation to the RMS value of
currents before voltage dip occurrence. All induction motors
were disconnected by contactors (measured control voltage
was 71% of nominal voltage), although the disconnection was
not necessary for the induction motors protection.
IL1_6kV_cel10/kA
2
1
-0,07
-0,06
-0,05
-0,04
-0,03
-0,02
-0,01
-0,00
0,01
0,02
0,03
t/s
-0,07
-0,06
-0,05
-0,04
-0,03
-0,02
-0,01
-0,00
0,01
0,02
0,03
t/s
-0,06
-0,05
-0,04
-0,03
-0,02
-0,01
-0,00
0,01
0,02
0,03
t/s
0
IL2_6kV_cel10/kA
2
1
0
IL3_6kV_cel10/kA
2
1
-0,07
0
+90°
+90°
IL3_6kV_cel10
IL2_6kV_cel10
IL2_6kV_cel10
±180°
IL2_6kV_cel18
IL1_6kV_cel18
IL3_6kV_cel18
IL3_6kV_cel10
IL1_6kV_cel10
IL3_6kV_cel18
IL2_6kV_cel18
0° ±180°
0°
IL1_6kV_cel18
U1/kV
3
IL1_6kV_cel10
2,7 kA
2
-90°
2,7 kA
-90°
Fig. 7. Example of recorded RMS values of secondary side currents of 35/6
kV transformer
1
-0,025
-0,000
0,025
0,050
0,075
0,100
0,125
t/s
0
U2/kV
3
V. CONCLUSION
2
1
-0,025
-0,000
0,025
0,050
0,075
0,100
0,125
t/s
-0,025
-0,000
0,025
0,050
0,075
0,100
0,125
t/s
0
U3/kV
3
2
1
0
+90°
+90°
U1
U1
U2
U2
±180°
0° ±180°
0°
U3
U3
4,0 kV
-90°
4,0 kV
-90°
Fig. 6. Example of recorded RMS values of 6 kV phase voltages
Voltage dips are probably the most important power quality
problem, especially for industrial customers having sensitive
electrical equipment. Examples of such sensitive equipment
are DC and AC drives, induction motors and its contactors.
Often disconnection of all production lines caused by voltage
dips can generate large financial losses.
That is the reason for a continuous research of voltage dip
phenomena in transmission and distribution network and their
consequences in industrial facilities and electrical equipment.
Faults in power system network cannot be eliminated, but
their influence on power quality can be reduced with better
protection coordination and protection response time
shortening. On the other side, customers have to improve the
ride-through capability of the sensitive equipment in their
facilities.
In this work the practical method for the calculation of
voltage dips influence zone and propagation through industrial
facility is shown on the example of a large cement factory.
The experimental check done by complex measurements
confirms correctness of such approach.
VI. REFERENCES
[1]
G. Yalcinkaya, M.H.J. Bollen, P.A. Crossley, “Characterization of
Voltage Sags in Industrial Distribution Systems”, IEEE Trans. Ind.
Applications, vol. 34, no. 4, pp. 682-688, July/August 1998
[2]
[3]
[4]
[5]
[6]
J. Lamoree, D. Mueller, P. Vinett, W. Jones, M. Samotyj, “Voltage Sag
Analysis Case Studies”, IEEE Trans. Ind. Applications, vol. 30, no. 4,
pp. 1083-1089, July/August 1994
Conrad St. Piere, “Don't let power sags stop your motors”, Plant
engineering, pp. 76-80, September 1, 1999.
Mark McGranaghan, “The Economics of Custom Power”, Presentation
from IEEE 2003 T&D Show, September, 2003.
M.R. Qader, M.H.J. Bollen, R.N. Allan, “Stochastic Prediction of
Voltage sags in a Large Transmission System”, IEEE Trans. Ind.
Applications, vol. 35, no. 1, pp. 152-162, January/February 1999
www.fractal.hr
VII. BIOGRAPHIES
Ranko Goic, Ph.D., born on the island of Brac,
Croatia, on April 11, 1969. He graduated from the
Faculty of Electrical Engineering, Mechanical
Engineering and Naval Architecture, University of
Split, where he also received his Ph.D. degree in
2002. Ever since graduation, he has been working
at the same faculty, in the Power System
department. His main research interests are the
power system network analysis and power system
planning and optimization. His research and
engineering interests are directed towards design of software tools for network
analysis and power system planning, which are in operative use in Croatia and
Bosnia and Herzegovina. He has also been engaged in many research and
practical investigation projects for the Croatian Power System Utility. He is a
member of IEEE and Croatian Committee of CIGRE.
Marko Lovric, B.Sc., born in Livno, Bosnia and
Herzegovina, on April 19, 1949. He graduated from
the Faculty of Electrical Engineering, Mechanical
Engineering and Naval Architecture, University of
Split in 1972. He has been working in Croatian
Power System Utility (HEP) from 1974 as operative
dispatcher, local dispatching centre manager and
general manager of HEP Transmission System
Operator, South Department. His interests include
planning, control and expansion of power system. He
is a member of Croatian Committee of CIGRE.
Eugen Mudnic, M.Sc, born in Split, Croatia, on
May 24, 1968. He graduated from the Faculty of
Electrical Engineering, Mechanical Engineering and
Naval Architecture, University of Split, where he
also received his M. Sc. degree in 2001. He has been
working at Fractal Split, Siemens PSE, and now he
is working on his Ph.D. at FESB Split & CERN
Geneve. His main research interests are the power
system network
analysis,
simulation
and
optimization. He is also working on analysis and
simulation of computational grid systems. He is a
designer of software tools for network analysis and power system planning,
which are in operative use in Croatia and Bosnia and Herzegovina. He is a
member of Alice offline-computing group at CERN.